EP1574911A1 - Appareil de développement pour le développement sous pression et avec un révélateur magnétique à un composant - Google Patents

Appareil de développement pour le développement sous pression et avec un révélateur magnétique à un composant Download PDF

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Publication number
EP1574911A1
EP1574911A1 EP04029559A EP04029559A EP1574911A1 EP 1574911 A1 EP1574911 A1 EP 1574911A1 EP 04029559 A EP04029559 A EP 04029559A EP 04029559 A EP04029559 A EP 04029559A EP 1574911 A1 EP1574911 A1 EP 1574911A1
Authority
EP
European Patent Office
Prior art keywords
developer
toner
image
developing
carrying member
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04029559A
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German (de)
English (en)
Inventor
Hikaru Osada
Kouichi Okuda
Yasushi Shimizu
Yasunori Chigono
Kena Ogawa
Shuji Moriya
Kazunari Hagiwara
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Canon Inc
Original Assignee
Canon Inc
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Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Publication of EP1574911A1 publication Critical patent/EP1574911A1/fr
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/083—Magnetic toner particles
    • G03G9/0836—Other physical parameters of the magnetic components
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/083—Magnetic toner particles
    • G03G9/0837—Structural characteristics of the magnetic components, e.g. shape, crystallographic structure

Definitions

  • the present invention relates to a developing apparatus for developing an electrostatic latent image formed on an image bearing member, with the use of developer. More specifically, it relates to a developing apparatus of a contact type, which develops an electrostatic latent image formed on an image bearing member, with the use of single-component developer.
  • This type of a developing apparatus can be used as the developing means for a process cartridge for developing an image bearing member such as an electrophotographic photosensitive member, an electrostatically recordable dielectric member, etc., and also, as the developing means for an image recording apparatus (image forming apparatus) such as a copying machine, a printer, etc.
  • an image recording apparatus image forming apparatus
  • an electrostatic latent image formed on an electrophotographic photosensitive member, as a member (image bearing member) on which an image is formed is developed with the use of single-component developer.
  • the single-component developing method there has been widely known (1) a nonmagnetic developing method of a contact type, and (2) a magnetic developing method of a noncontact type.
  • a developing method which develops an electrophotographic latent image by coating a development roller (developer bearing member), having a dielectric layer, with nonmagnetic developer, and placing the layer of the nonmagnetic developer on the development roller in contact with the peripheral surface of the photosensitive member (for example, Japanese Laid-open Patent Application 2001-92201).
  • the developer in a developing apparatus (which hereinafter may be referred to as developing device) is supplied to a development roller with the use of a mechanical stirring system, or gravity. Further, a developing apparatus is provided with an elastic roller, which conveys the developer, and supplies the development roller with the developer.
  • the elastic roller is also given the role of removing the developer remaining on the development roller, that is, the developer which did not transfer onto the photosensitive member. Between the substrate of the photosensitive member and the development roller, DC bias is applied.
  • This method uses single-component magnetic developer, and a development sleeve (development bearing member) containing a magnet.
  • Single-component magnetic developer is coated on the peripheral surface of the development sleeve, and the development roller is positioned so that a predetermined minute gap is present between the developer layer on the development roller and the peripheral surface of the photosensitive member.
  • a latent image on the peripheral surface of the photosensitive member is developed by causing the developer to fly (jump) across this minute gap.
  • the developer in the developing device is conveyed to the development sleeve by the mechanical stirring system or gravity, it is coated on the development sleeve by a certain amount of the magnetic force from the magnet.
  • the body of the developer on the development roller is formed by a regulating member into a uniform layer of the developer with a predetermined thickness to be used for development.
  • a regulating member is used for another purpose in the development station. More specifically, the magnetic force is utilized for preventing the formation of unsatisfactory images, for example, an image suffering from the so-called fog attributable to the transfer of developer onto the unintended portions (non-image portion, that is, white (blank) areas of image) of a recording medium, in the development station.
  • the developer is subjected to the magnetic force from the magnet in the development roller, which acts in the direction to pull the developer toward the development roller.
  • the DC bias is set to a value between the potential level of a developer attracting point (image portion) and the potential level of a developer repelling point (non-image portion).
  • the potential level of the development bias sometimes exceeds that of the image portion, and sometime falls below that of the non-image portion, causing thereby the developer to shuttle between the development roller and the image portion, and also, between the development roller and non-image portion, while developing the latent image on the photosensitive member.
  • the abovementioned nonmagnetic contact developing method (1) has been problematic in that it is inferior in terms of the fog prevention. That is, as toner is repeatedly stripped away from the development roller by the elastic roller, it deteriorates in certain properties, for example, the ability to be frictionally charged, contributing thereby to the exacerbation of the fog.
  • fog means the phenomenon that toner slightly adheres to the white (unexposed) areas, that is, the areas to which toner was not intended to be adhered, causing the resultant image to appear as if its white (blank) portions were soiled.
  • the means for preventing the toner from deteriorating certain in properties it is possible to reduce the amount of the friction generated by the elastic roller.
  • Ghost means the phenomenon that the pattern formed on the peripheral surface of the development roller by toner consumption during a given image developing rotation of the development roller emerges like a ghost across the half-tone areas of the portion of an image being formed during the following rotations of the development roller.
  • the ghostly pattern repeats itself across an image (transfer medium) with intervals which match the circumferential dimension of the development roller, resulting in the formation of an image irregular in density.
  • the presence of a ghost means that a certain amount of the residual toner was not stripped from the development roller.
  • the nonmagnetic contact developing method in accordance with the prior art is not desirable, from the standpoint of the toner deterioration in certain properties, in that the toner on the development roller is continuously subjected to the friction caused by the elastic roller.
  • the prevention of a fog and the prevention of a ghost contradict each other, but also, the prevention of a ghost has its own contradictory factors.
  • the toner deterioration also created the problem that toner was easily affected by being circulated in the developing device. More specifically, as toner was circulated, mechanically or by gravity, in the developing device, the body of toner in the adjacencies of the peripheral surface of the development roller was barely moved; in other words, the areas in which toner was not replaced were created in the adjacencies of the peripheral surface of the development roller. Meanwhile, the toner in the area in which toner was circulated was deteriorated by a certain amount in certain properties.
  • the usage of the cleaner-less method allowed paper dust to enter the elastic roller (sponge roller), resulting sometimes in the formation of such an image that suffered from the defects which repeated themselves, with such intervals that matched the circumferential dimension of the elastic roller.
  • the edges of the high density areas are more densely developed, in particular, on the downstream side in terms of the processing direction, whereas the edges of the half-tone areas adjacent to the high density areas are lightly developed.
  • the cause for this phenomenon is thought to be that the development roller is not placed in contact with the photosensitive member, and also, that for the development of a latent image on the photosensitive member, developer particles are made, by the AC electrical field, to shuttle between the development roller and photosensitive member. More specifically, in the development station, toner particles are moved in the direction parallel to the plane of the development roller (photosensitive member); not only are they moved to the edges of the high density areas from within the high density areas, but also, from outside the high density areas. As a result, image defects such as the above described ones occur.
  • a cleaner-less image forming apparatus employs the noncontact developing method. Therefore, it is relatively low in its performance to recover the toner on the photosensitive drum, suffering therefore the problem that the transfer residual toner forms ghosts in the solid white areas and half-toner areas of an image as the image is developed, as well as the problem that an image having black spots (which hereinafter) will be referred to as white spots) in its solid black areas is formed. It is thought that these white spots are likely to be formed as paper dust enters the gap between the development roller and photosensitive drum, because the presence of paper dust between the development roller and photosensitive drum allows the occurrences of bias leak between the development roller and photosensitive drum, allowing thereby the latent image on the photosensitive drum to increase in potential level (shift in negative direction).
  • the contact developing apparatus in accordance with the prior art sometimes produces an image having defects in its solid white areas. These defects repeat themselves across the image (transfer medium) with such intervals that match the dimension of the development roller in terms of the circumferential direction, and are as wide as several millimeters.
  • the cause of these defects is thought to be that as developer particles enter the contact area between the development roller and photosensitive drum, they are pressed by the roller and drum, being thereby more firmly adhered to the development roller in terms of electrostatic adhesion than in the case of the noncontact developing apparatus.
  • the primary object of the present invention is to solve the above described problems to provide a developing apparatus superior to a developing apparatus in accordance with the prior art, in that it does not suffer from the above described problems.
  • Another object of the present invention is to prevent developer from deteriorating in certain properties, in order to provide a developing apparatus which does not yield an image suffering from fog.
  • Another object of the present invention is to provide a developing apparatus which does not yield an image having defects in its half-tone areas.
  • Another object of the present invention is to provide a developing apparatus which does not yield an image suffering from ghosts.
  • Another object of the present invention is to provide a developing apparatus which does not yield an image having defects in its solid white areas.
  • FIG. 1 is a schematic drawing of an image recording apparatus (image forming apparatus) employing one of the developing apparatuses in accordance with the present invention, showing the general structure thereof.
  • This image forming apparatus is a laser printer of a transfer type, which employs an electrophotographic process.
  • the image bearing member 1 in this embodiment is in the form of a rotatable drum (hereinafter, it will be referred to as photosensitive drum). It is a photosensitive member of an OPC type, and its inherent polarity is negative. It is 24 mm in diameter.
  • This photosensitive drum 1 is rotationally driven in the clockwise direction indicated by an arrow mark, at a constant peripheral velocity (process speed PS; printing speed) of 85 mm/sec.
  • a charge roller As a charging means.
  • This charge roller 2 is an electrically conductive elastic roller, comprising a metallic core 2a and an electrically conductive elastic layer 2b. It is kept pressed on the photosensitive drum 1 with the application of a predetermined amount of pressure, forming a charging station n between the charge roller 2 and photosensitive drum 1. In this embodiment, the charge roller 2 is rotated by the rotation of the photosensitive drum 1.
  • Designated by a referential symbol S1 is a power source for applying charge bias to the charge roller 2.
  • DC voltage the potential level of which is higher than the charge start voltage
  • a DC voltage of -1,300 V is applied as the charge bias to the charge roller 2, which is in contact with the photosensitive drum 1, in order to uniformly charge the peripheral surface of the photosensitive drum 1 to a potential level of -700 V (potential level of unexposed point).
  • a laser scanner (exposing apparatus) having laser diodes, polygon mirrors, etc.
  • This laser beam scanner is for outputting a beam L of laser light, while modulating it in intensity with sequential electrical digital image formation pixel signals, in order to scan (expose) the uniformly charged peripheral surface of the aforementioned rotational photosensitive drum 1.
  • the intensity of the beam L of the laser light is adjusted so that as a given one of the numerous points of the peripheral surface of the photosensitive drum 1 is exposed to the beam L of laser light, the potential level of this point of the photosensitive drum 1 changes to -150 v.
  • Designated by a referential number 60A is a developing apparatus (developing device) in the first version of the image forming apparatus which will be described later.
  • the toner t is frictionally charged, and is made to develop, in the development station, the electrostatic latent image on the photosensitive drum 1, by the development bias applied between the developing sleeve 60b, as a developer bearing member (developer bearing carrying member), and the photosensitive drum 1, by the development bias application power source S2.
  • the developing apparatus 60A will be described later in detail when the following versions of the embodiments of the present invention, and the versions of the comparative embodiments, are described.
  • a transfer roller As a transferring means of a contact type, the electrical resistance of which is in the mid range.
  • the transfer roller 6 is kept in contact with the photosensitive drum 1 with the application of a predetermined amount of pressure, forming a transfer nip b.
  • a recording medium P as an object on which recording is made, is delivered with a predetermined timing from an unshown sheet feeding station, while a predetermined transfer bias is applied to the transfer roller from a transfer bias application power source S3.
  • a transfer bias application power source S3 As a result, the toner image on the photosensitive drum side are sequentially and continuously transferred onto the surface of the transfer medium P, as the transfer medium is conveyed through the transfer nip b.
  • the transfer roller 6 in this embodiment comprises: a metallic core 6a, and a layer 6b of foamed substance, the electrical resistance of which is in the mid range.
  • the electrical resistance of the transfer roller 6 is 5x10 8 ⁇ .
  • the transfer is caused by applying a voltage of +2.0 kV to the metallic core 6a.
  • the transfer medium P is conveyed through the transfer nip b while remaining pinched by the transfer roller 6 and photosensitive drum 1.
  • the toner image on the peripheral surface of the photosensitive drum 1 is continually transferred onto the surface of the transfer medium P by the electrostatic force and the pressure in the transfer nip b.
  • Designated by a referential number 7 is a fixing apparatus which employs a thermal fixing method, or the like. After the transfer of the image on the peripheral surface of the photosensitive drum 1 onto the transfer medium P having been delivered to the transfer nip b, the transfer medium P is separated from the peripheral surface of the photosensitive drum 1, and is introduced into the fixing apparatus 7, in which the toner image is fixed to the transfer medium P. Thereafter, the transfer medium P is discharged as a copy from the main assembly of the image forming apparatus.
  • Designated by a referential number 8 is a cleaning apparatus (drum cleaner) for cleaning the photosensitive drum 1.
  • the cleaning apparatus 8 scrapes the peripheral surface of the photosensitive drum 1, with the cleaning blade 8a, removing thereby the residual toner, or the toner remaining on the peripheral surface of the photosensitive drum 1, from the peripheral surface of the photosensitive drum 1, after the image transfer, and recovers the toner it removed, into a waste toner container 8b.
  • the photosensitive drum 1 After the cleaning of the peripheral surface of the photosensitive drum 1, the photosensitive drum 1 is recharged by the charging apparatus 2, and used for the next image formation.
  • Designated by a referential symbol 9A is a process cartridge, which comprises: a cartridge in which the photosensitive drum 1, charge roller 2, developing apparatus 60A, and drum cleaner 8 are integrally disposed, and which is removably mountable in the main assembly of the image forming apparatus.
  • FIG. 2 is a image recording apparatus employing the developing apparatus in the second embodiment of the present invention, showing the general structure thereof.
  • the image recording apparatus in this embodiment is a laser printer of a transfer type, which employs an electrophotographic process as well as a toner recycling process (cleaner-less system).
  • cleaning-less system a toner recycling process
  • the most essential difference of the image forming apparatus in this embodiment from the image forming apparatus in the first embodiment is that this image forming apparatus is not equipped with the drum cleaner 8 shown in Figure 1, and the transfer residual toner is recycled. In order to prevent the transfer residual toner from derogatorily affecting the other processes such as the charging process, the transfer residual toner is re-circulated and is recovered into the developing apparatus 60A. More specifically, the following structural changes are made to the image forming apparatus in the first embodiment.
  • a charge roller 2 identical to the charge roller 2 in the first embodiment is employed. In this embodiment, however, the charge roller 2 is independently driven. The revolution of the charge roller 2 per unit length of time is adjusted so that the peripheral velocity of the charge roller 2 matches the peripheral velocity (process speed) of the photosensitive drum 1. With the charge roller 2 being driven independently from the photosensitive drum 1, it is assured that the charge roller 2 remains in contact with the photosensitive drum 1 and a charge roller contacting member 20 to charge the toner to the negative polarity (normal polarity). Further, another reason the charge roller 2 is providing with the contacting member 20 is for preventing the charge roller 2 from remaining contaminated.
  • the contacting member 20 is formed of a polyimide film with a thickness of 100 ⁇ m, and is placed in contact with the charge roller 2 so that a linear pressure of 10 (N/m) will be maintained between the contacting member 20 and charge roller 2.
  • the reason for the usage of polyimide is that polyimide has the property of frictionally charging toner to the negative polarity.
  • Designated by a referential symbol 9B is a process cartridge in which the photosensitive drum 1, charge roller 2, charge roller contacting member 20, and developing apparatus 60A are integrally disposed, and which is structured so that it can be removably mounted into the main assembly of the image forming apparatus.
  • a development sleeve as a rotatable developer bearing member (developer bearing-carrying member), in which a magnetic roll 60a as a magnetic field generating means is solidly and nonrotationally disposed.
  • the development sleeve 60b comprises: an aluminum cylinder 60b1, and a layer 60b2 of nonmagnetic and electrically conductive substance placed on the peripheral surface of the aluminum cylinder 60b1. It is kept in contact with the photosensitive drum 1 with the application of a predetermined amount of pressure.
  • the pressure between the photosensitive drum 1 and the developing sleeve 60b is adjusted at 200 N/m (drawing pressure).
  • the pressure between the photosensitive drum and the developing sleeve is preferably 50 - 3000 N/m (drawing pressure).
  • the drawing pressure is a pressure value corresponding to a line pressure and is a force per 1m required to draw a SUS (stainless steel) plate of 30 ⁇ m thick sandwiched between two SUS plates each having a thickness of 30 ⁇ m.
  • the drawing pressure is not less than 3000 N/m, remarkable scraping of the surface of the image bearing member and/or deterioration of the developer, and therefore, image defects result. If it is not more than 50 N/m, the size of the developing zone is not sufficient, with the result that transition of the developer from the developer carrying member onto the image bearing member is not sufficient, and therefore, image defects result.
  • the developing sleeve 60b of this embodiment is manufactured by kneading a material for the non-magnetic electroconductive elastic layer 60b2, extruding the kneaded material, bonding the extruded material on an aluminum sleeve 60b1 into a layer 60b2, and abrading the bonded layer 60b2 into a thickness of 500 ⁇ m.
  • the developing sleeve 60b has a microhardness of 95°, and a surface roughness Rz of 3.8 ⁇ m and a surface roughness Ra of 0.6 ⁇ m.
  • the elastic layer preferably has a microhardness of 40 - 98°.
  • the surface hardness has been measured using a microhardness meter Asker MD- 1F360A, available from Kobunshi Kabushiki Kaisha, Japan. If the microhardness is not more than 40, the scraping and damage of the surface of the elastic layer is extremely remarkable due to the sliding contact with the regulating member, the image bearing member and the like, and therefore, image defects result. For this reason, it is preferably not less than 40. If, however, it exceeds 98, the scraping and/or damage of the image bearing member occurs due to the sliding contact with the image bearing member resulting in image defects. Therefore, it is preferably not more than 98.
  • the surface roughness has been measured using a surfcorder SE3400, available from KOSAKA KENKYUSHO Kabushiki Kaisha, Japan, with contact detecting unit PU- DJ2S under the condition of the measurement length of 2.5 mm, the perpendicular direction magnification of 2000 times, the horizontal direction magnification of 100 times, the cut-off level of 0.8 mm and the filter setting of 2CR, and the leveling setting of front data.
  • a magnet roller 60a is a fixed magnet functioning as magnetic field generating means for generating magnetic forces at the predetermined positions on the developing sleeve 60b. It generates a magnetic flux density having a peak density of 700 G (absolute value) at each of the positions of a developing zone a, a feeding portion, a supply portion and a collecting portion.
  • the maximum value of the intensity of the magnetic flux density in the direction perpendicular to the surface of the developer carrying member is preferably approximately 200 - 1500 G, and further preferably 500 - 900 G.
  • the peak densities of the magnetic poles are generated at the positions of the developing zone, the collecting portion, the supply portion, the feeding portion and the developing zone in the order named.
  • the toner carried to the developing zone is used for development at the developing zone, and the toner not consumed in the developing zone is collected back into the developing container by a collecting portion disposed downstream of the developing zone.
  • a collecting portion disposed downstream of the developing zone.
  • means is provided to prevent blowing of the toner from the inside of the developing device.
  • the toner reaching the collecting portion is fed to the supply portion disposed downstream of the collecting portion in the developing container with respect to the developer carrying direction.
  • the toner having reached the collecting portion is mixed with the supplied toner, and is carried to a feeding portion disposed downstream of the supply portion, and is again fed to the developing zone, thus accomplishing continuous toner supply to the developing zone.
  • the magnetic flux density has been measured, in this embodiment, using Gauss meter, series 9900 with probe A-99 - 153, available from Bell.
  • the Gauss meter has an axial probe in the form of a rod connected to the main assembly of the Gauss meter.
  • the developing sleeve 60b is fixed in a horizontal position, and the magnet roller 60a is rotatable.
  • the probe taking a horizontal attitude is perpendicularly disposed with a small gap, and the center of the developing sleeve 60b and the center of the probe are placed in the same horizontal plane. They are placed at such fixed positions, and the magnetic flux density is measured.
  • the magnet roller 60a and the developing sleeve 60b are substantially concentric, and therefore, it is considered that clearance between the developing sleeve 60b and the magnet roller 60a are constant irrespective of the peripheral positions on the magnet roller 60a.
  • the measurement covers all the positions in the circumferential direction of the developing sleeve 60b. From the obtained magnetic flux density data in the peripheral directions, the peak strengths at each of the positions has been determined.
  • the resistance value of the electroconductive elastic layer provided at that surface of the developing sleeve is preferably 10 2 - 10 8 ⁇ cm. If it is less than 2 ⁇ cm, electrical leakage and/or decrease of the surface potential occurs with the result of image defect (fog) due to transfer of the toner to a non-printing portion of the image bearing member. If it exceeds 10 8 ⁇ , an effective bias level of the developing bias is so small with the result of production of fog and/or the reduction of the image density.
  • an electroconductive elastic layer is formed on the sleeve base layer, and in the state, a weight of 300 g is imparted at the opposite ends of the sleeve base layer.
  • a bare tube of aluminum having a diameter which is the same as that of the image bearing member is contacted thereto, and then, the aluminum bare tube is rotated, by which the elastic sleeve is driven by the aluminum bare tube.
  • a voltage of -400 V is applied between the core metal and the aluminum bare tube, and the current flowing through the aluminum bare tube is measured as a current flowing through the electroconductive elastic layer.
  • the resistance value of the electroconductive elastic layer is determined from the voltage applied to the sleeve base layer and the current through the aluminum bare tube.
  • Thickness of electroconductive elastic layer of elastic developing sleeve is a thickening of electroconductive elastic layer of elastic developing sleeve.
  • the thickness of the electroconductive elastic layer as the electroconductive developing sleeve is preferably not more than 50 - 2000 ⁇ m. If it is not more than 50 ⁇ m, the surface of the image bearing member is scraped and/or damaged with the result of image defect, and therefore, it is preferably not less than 50 ⁇ m. If it is not less than 2000 ⁇ m, the magnetic force applied to the surface of the image bearing member from the fixed magnetic field generating device disposed therein is so small that amount of the developer supplied is not enough to provide satisfactory images. Therefore, it is preferably not more than 2000 ⁇ m.
  • the toner t1 which is an one component magnetic toner t1 (developer) and is produced through a suspension polymerization method and has an average circularity of 0.976.
  • the average circularity is used as a simple methods quantitatively expressing the configurations of the toner particles.
  • the average circularity has been determined using a flow type particle image analyzing apparatus available from Toa-Iyo Denshi Kabushiki Kaisha, Japan (FPIA- 2100).
  • Circularities (Ci) particles of a group of the particles having the circle-corresponding diameter of not less than 3 ⁇ m are obtained using the following equation (1), and the total sum of the circularities of all of the particles having been subjected to such equation (2):
  • Circularity (Ci) (length of circumference of a circle having a projection area which is the same as the particle) /(length of circumferene of a circle of a projection of the particle)
  • the developer contains the same weights of the developer and magnetic particles and the binder resin to provide magnetic particles which can be conveyed by sufficiently strong magnetic force.
  • the amount of the magnetic particle is 100 parts-by-weight relative to 100parts-by-weight of the binder resin, but in the amount of the magnetic magnetic particle relative to the binder resin 100 parts-by-weight may be 70 - 120 parts-by-weight with which the advantages effects of the present invention can be provided.
  • the average particle size (D4) of the toner is 6 ⁇ m.
  • the density ⁇ of magnetic toner is 1.6.
  • the density of magnetic toner means a true density of the particle, and the true density has been measured using a dry type density meter Acupic 1330, available from Shimazu Seisakusho, Japan.
  • the amount of magnetization of the magnetic toner ⁇ is 30Am 2 /kg. In this embodiment, the amount of magnetization of the magnetic toner has been measured using vibration magnetic force meter VSM-3S- 15, available from Toei Kogyo Kabushiki Kaisha, under 1 K oersted magnetic field.
  • An index indicative of an amount of the magnetic material exposed at the surface of the toner particles may be a ratio (B/A) between the content (A) of carbon element existing at the surface of the magnetic toner particle and the content of iron element (B), measured by X-ray photoelectron spectrum analysis (as disclosed in Japanese Laid-open Patent Application2001-235897 or the like).
  • the (B/A) of the toner t1 is 0.001.
  • Such magnetic polymerized toner may be produced through the methods disclosed in Japanese Laid-open Patent Application2001-235899, for example.
  • the toner t1 is subjected to a layer thickness regulation of the regulating blade 60c (developer amount regulating member) for regulating the amount of the developer on the developing sleeve, and is also subjected to triboelectric charging.
  • regulating blade 60c developer amount regulating member
  • triboelectric charging Designated by 60d is a stirring member for circulating the toner in the developing container 60e and feeding the toner sequentially into magnetic force reaching ranges around the surface of the sleeve.
  • the developing device 60A of in this example employs a regulating blade 60c which has a length of a free part of 2.5 mm and which is placed with a drawing pressure of 55 (N/m).
  • the length of the free part on the blade is a length from the contact portion of the regulating blade 60c relative to the developing sleeve 60b.
  • the toner t1 applied on the developing sleeve 60b is fed to the developing zone (developing zone portion) a where the developing sleeve 60b is opposed to the surface of the photosensitive drum 1, by the rotation of the developing sleeve 60b.
  • the developing sleeve 60b its supplied with the developing bias voltage (DC voltage -450V) from a developing bias applying voltage source S2.
  • the peripheral speed of developing sleeve 60b is 1.2 times the peripheral speed of the photosensitive drum 1. By doing so, the electrostatic latent image on the photosensitive drum 1 is developed with the toner t1 (reverse development).
  • the peripheral speed of the developing sleeve 60b relative to the photosensitive drum 1 is 1.2times in this embodiment, but it may be different within a range of 1.0 - 2.0times with which the advantageous effects of the present invention may be provided.
  • the structure of the developing device in this embodiment is substantially the same as that of the developing device 60A of Embodiment 1, but the toner t2 used here is different from the only used in Embodiment 1.
  • the toner t2 is an one component magnetic toner t2 produced by mixing and kneading binder resin, magnetic particle and charge control material through a surface improvement treatment and classification. It contains externally added material for fluidization (pulverization method known by Japanese Laid-open Patent Application 2002-341590, for example.
  • the developer contains the same weights of the magnetic particles and the binder resin to provide magnetic particles which can be conveyed by sufficiently strong magnetic force.
  • the toner has an average particle size (D4) of 6 ⁇ m and an average circularity 0.968 determined by the methods described in the foregoing.
  • the structure of the developing device in this embodiment is substantially the same as that of the developing device 60A of Embodiment 1, but the toner t3 used here is different from the only used in Embodiment 1.
  • the toner t3 is an one component magnetic toner produced by mixing and kneading binder resin, magnetic particle and charge control material through a surface improvement treatment and classification. It contains externally added material for fluidization (pulverization method), similarly to Embodiment 2.
  • the developer contains the same weights of the magnetic particles and the binder resin to provide magnetic particles which can be conveyed by sufficiently strong magnetic force.
  • the toner has an average particle size (D4) of 8 ⁇ m and an average circularity 0.950. Determined by the methods described in the foregoing.
  • FIG. 4 is a schematic view of the developing apparatus of this embodiment.
  • the magnet roller 60p used in this embodiment is different from the magnet roller 60a used in the developing device 60A of Figure 1 in the number of the magnetic poles and the surface magnetic flux densities.
  • a magnet roller 60a is a fixed magnet functioning as magnetic field generating means for generating magnetic forces at the predetermined positions on the developing sleeve 60b.
  • the magnet roller 60p generates peak densities magnetic flux densities of 300 G (absolute value) at the feeding portion and the supply portion.
  • the used toner t4 is one component magnetic toner t4 and is produced by mixing and kneading binder resin, magnetic particle and charge control material through a pulverization and classification. It contains externally added material for fluidization (pulverization method).
  • the developer contains the same weights of the magnetic particles and the binder resin to provide magnetic particles which can be conveyed by sufficiently strong magnetic force.
  • the toner has an average particle size (D4) of 8 ⁇ m and an average circularity of 0.945, determined by the methods described in the foregoing.
  • the ratio (B/A) defined in the foregoing is 0.05.
  • FIG. 3 is a schematic view of an image recording device using a developing device of comparison example of scheme 1 (a drum cleaner of Figure 1 is employed).
  • the developer use to hear is toner t4 which will be described hereinafter.
  • the developing sleeve 60f compresses an aluminum cylinder and a non-magnetic electroconductive layer (unshown) on the aluminum cylinder and is disposed with a gap of 300 ⁇ m from the photosensitive drum 1.
  • the developing sleeve 60f has a microhardness of 100°, a surface roughness Rz home 11.5 ⁇ m and a surface roughness Ra 1.5 ⁇ m.
  • the toner t4 filled in the developing device 60B is carried on the developing sleeve 60f while being subjected to the magnetic force provided by the magnet roller 60a, during which a layer thickness of the toner t4 is regulated by the regulating blade 60g and and the toner t4 is triboelectrically charged.
  • Designated by 60d is a stirring member for circulating the toner in the developing container 60e and feeding the toner sequentially into magnetic force reaching ranges around the surface of the sleeve.
  • the developing device 60B of this embodiment employs a regulating blade 60g which has a length of a free part of 1.2 mm and which is placed so that the drawing pressure is 30 (N/m).
  • the toner t4 applied on the developing sleeve 60f is carried by the rotation of the sleeve 60a to the developing zone (developing zone portion) where the sleeve 60f it opposed to the surface of the photosensitive drum 1.
  • the sleeve 60a is supplied with a developing bias voltage (DC voltage of -450V superimposed with AC voltage of 1.8 kVpp, 1.6 kHz).
  • the developing sleeve 60f is rotated at a peripheral speed which is 1.2times the peripheral speed of the photosensitive drum 1.
  • the electrostatic latent image on the photosensitive drum 1 is developed with the toner t4 (reverse development).
  • the developer is toner t4.
  • the toner t4 is the same as the toner used in Embodiment 4.
  • the fundamental structure of the developing device of comparison example 2 is substantially the same as that of comparison example 1, namely, developing device 60B ( Figure 3), but is different in the magnet roller enclosed in the developing sleeve 60f.
  • the magnet roller used in this embodiment is the same as the magnet roller 60p.
  • the developing device of comparison example 3 is the same as the developing device 60B of comparison example 1 except for the following.
  • the developing sleeve 60f is contacted the photosensitive drum 1 with a predetermined pressure.
  • the pressure is such that drawing pressure between the photosensitive drum 1 and the developing sleeve 60f is 50 N/m.
  • the developing bias applied is only DC voltage of - 450V.
  • Figure 5 is a schematic view of an image recording device using the developing device of comparison example 4 of scheme 1.
  • the developing sleeve 60r comprises an aluminum cylinder 60r1 and a non-magnetic electroconductive elastic layer 60r2 and is contacted to the photosensitive drum 1 with a predetermined pressure.
  • the pressure is 200N/m in the drawing pressure.
  • the electroconductive elastic layer 60r2 produced by kneading materials, and extruding the kneaded material. It is bounded on the aluminum sleeve 60r1 with the thickness of 500 ⁇ m and is then abraded, thus providing the developing sleeve 60r.
  • the microhardness thereof is 94°, and surface roughness Ra thereof is 1.2 ⁇ m.
  • the magnet roller 60q is a multi-pole magnet roller having 8 poles at regular intervals.
  • the peak densities of the magnetic flux densities provided are 300G (absolute value).
  • the magnet roller 60q is rotated in the direction opposite the rotational direction of the developing sleeve 60r in the same rotational speeds.
  • the toner t4 is carried on the developing sleeve 60 r while being subjected to the magnetic force provided by the magnet roller 60 p, during which a layer thickness of the toner t4 is regulated by the regulating blade 60 c, and the toner t4 is triboelectrically charged.
  • Designated by 60d is a stirring member for circulating the toner in the developing container 60e and feeding the toner sequentially into magnetic force reaching ranges around the surface of the sleeve.
  • the developing device 60 D of in this embodiment employs a regulating blade 60c which has a length of a free part of 1.2 mm and which is placed with a drawing pressure of 30 N/m.
  • the toner t applied on the developing sleeve 60 r is carried by the rotation of the sleeve 60 r to the developing zone (developing zone portion) where the sleeve 60 r opposed to the surface of the photosensitive drum 1.
  • the sleeve 60r is supplied with a developing bias voltage DC voltage of -450V) from the developing bias applying voltage source S2.
  • the developing sleeve 60 r is rotated at a peripheral speed which is 1.2times the peripheral speed of the photosensitive drum 1. By doing so, the electrostatic latent image on the photosensitive drum 1 is developed with the toner t1 (reverse development).
  • Toner t4 is the same as with comparison example 1.
  • Japanese Patent Application Publication Hei 4 - 15949 discloses a developing device which is similar to the structure of this comparison example.
  • the developing device of comparison example 5 is different from the developing device 60A of Embodiment 1.
  • the photosensitive drum 1 and the developing sleeve 60b are placed with the gap of 200 ⁇ m therebetween, and the supplied developing bias comprises a DC voltage -450V and an AC voltage (rectangular wave, 800Vpp, 2000Hz) (proximity AC).
  • the regulating blade 60c is set with a drawing pressure of 30N/m, and the free part length thereof is 0.5 mm.
  • Japanese Laid-open Patent Application Hei 7 - 28335 discloses a developing device which it similar to the structure of the developing device of this example.
  • FIG. 5 is a schematic view of an image recording device using the developing device of comparison example 4 of scheme 1.
  • Designated by 60h is a developing roller comprising the core metal 60h1 and an electroconductive elastic layer 60h2 thereon.
  • Designated by 60k is an elastic roller comprising a core metal 60k1 and an elastic layer 60k2 thereon.
  • the developing roller 60h is contacted into the photosensitive drum 1 with up to determine depression corresponding to a drawing pressure of 20 N/m.
  • the elastic roller 60k is fixed with a predetermined distance between the shafts of the developing roller 60h and the elastic roller 60k, and the drawing pressure there between is 40 N/m.
  • the developing roller 60h is rotated to provide a peripheral speed which is 1.4times the peripheral speed of the photosensitive drum 1, and the elastic roller 60k is driven to rotate in the opposite peripheral direction document to the developing roller at the same rotational speed.
  • the rubber hardness of the developing roller 60h is 50° in ASKER- C hardness (500g) and is 42° in microhardness.
  • the stirring member 60d functions to supply the toner t5 to the elastic roller 60k. Furthermore, the elastic roller 60k functions to supply the toner t5 to the developing roller 60h by the rotation thereof.
  • the toner supplied to the surface of the developing roller 60h is regulated into a predetermined layer thickness and is triboelectrically charged by the regulating blade 60i, and the toner layer is fed to the developing zone.
  • the toner fed to the developing roller is used for developing the latent image on the photosensitive drum at the developing zone a.
  • the toner not consumed for the development and remaining on the developing roller 60h is scraped off by the elastic roller 60k, and is recirculated in the container 60e and is again applied on the surface of the developing roller 60h.
  • the applied developing bias comprises a DC voltage of- 450V which is applied to the developing roller core metal 60h1.
  • the elastic roller 60k and the regulating blade 60i are also supplied with the same developing bias.
  • the used toner t5 is one component magnetic toner t5 and is produced by mixing and kneading binder resin, magnetic particle and charge control material through a pulverization and classification. It contains externally added material for fluidization and charging particles m.
  • the average particle size (D4) of the toner is 8 ⁇ m.
  • Figure 7 is a schematic view of an image recording device using the developing device of comparison example 7 of scheme 1.
  • Designated by 60h is a developing roller comprising the core metal 60h1 and an electroconductive elastic layer 60h2 thereon.
  • Designated by 60j is a discharging sheet including an electroconductive sheet 60j2 which is lined with an elastic member 60j1.
  • the developing roller 60h is contacted into the photosensitive drum 1 with up to determine depression corresponding to a drawing pressure of 20N/m.
  • the discharging sheet 60j urged to the developing roller 60h with a predetermined pressure so that the drawing pressure is 55N/m.
  • the developing roller 60h is rotated to provide a peripheral speed which is 1.4times the peripheral speed of the photosensitive drum 1.
  • a feeding roller 60n is disposed to the developing roller without contact thereto and is rotated to provide the same peripheral speed as the developing roller 60h.
  • the rubber hardness of the developing roller 60h is 50° in ASKER- C hardness (500g) and is 42° in microhardness.
  • the stirring member 60d functions to supply the toner t5 to the feeding roller 60n.
  • the feeding roller 60n functions to supply the toner t5 to the developing roller 60h by the rotation thereof.
  • the toner supplied to the surface of the developing roller 60h is regulated into a predetermined layer thickness and is triboelectrically charged by the regulating blade 60i, and the toner layer is fed to the developing zone.
  • the toner fed to the developing roller is used for developing the latent image on the photosensitive drum 1 at the developing zone a.
  • the toner not consumed by the development and remaining on the developing roller 60h is electrically discharged by the discharging sheet 60j, and then is recirculated in the container 60e and is again applied on the developing roller 60h.
  • the applied developing bias comprises a DC voltage of- 450V which is applied to the developing roller core metal 60h1.
  • the feeding roller 60n and the regulating blade 60i are supplied with the same developing bias potential.
  • Toner t5 is the same as with comparison example 1.
  • Japanese Patent No.3225759 discloses a developing device of a structure similar to this example.
  • the developing apparatus of this Embodiment 5 is different from the developing device 60A of the Embodiment 1 in the developing bias applying voltage source S2.
  • the developing bias applying voltage source S2 of this embodiment applies the developing bias voltage of DC voltage -450V superimposed with an AC voltage in the form of a rectangular wave having a frequency of 1.2kHz and a peak-to-peak voltage of 300 V.
  • the developing apparatus of this Embodiment 6 is different from the developing device of the Embodiment 3 in the developing bias applying voltage source S2.
  • the developing bias applying voltage source S2 of this embodiment applies the developing bias voltage of DC voltage -450 V superimposed with an AC voltage in the form of a rectangular wave having a frequency of 1.2 kHz and a peak-to-peak voltage of 300 V.
  • the specific charge of the toner and the amount of the toner coating on the developing sleeve after the toner is regulated by the developing blade is measured in the following manner.
  • FIG. 8 shows an apparatus used in the measurement through the suction type Faraday gauge method, wherein the suction opening 11 is abutted to the developing sleeve or developing roller, and the developer is sucked to collect the toner on a filter 12 provided in an inner cylinder. At this time, the inner cylinder is electrostatically shielded from outside, and the amount Q (C) of electric charge of the developer accumulated here is measured by an electrometer 6517A, available from KEITHLEY Corp.
  • the weight M (g) of the sucked developer is calculated on the basis of the increase of the weight of the filter, and the area S (m2) from which the toner is sucked is measured, too. Then, the specific charge of the developer on the sleeve Q/M ( ⁇ C/g) and the amount of coating M/S (g/m 2 ) are calculated. For the measurement, an operation of the main assembly of the recording device is stopped during operation of solid white printing, and the measurement is carried out for the developing roller or developing sleeve.
  • Table 1 show the results of evaluations of the developing devices according to Embodiments 1 - 6, and the developing devices of comparison examples 1 - 7.
  • scheme 1 scheme 2 Emb. 1 0.976 0.001 29 10 G-G G G G G G G G G G G G G G G G G G G Emb. 2 0.968 0.01 32 9 G-G G C G G G G G G G G G G G G G Emb. 3 0.950 0.01 16 14 G-G G G G G G G G G G G G G G G G G G Emb. 4 0.945 0.05 16 14 G-G G G G G G G G G G G F G G G G G G Comp. Ex. 1 0.945 0.05 6 10 G-G G G G N N G G G N G G N Comp. Ex.
  • the coating amount 8 - 15 g/m 2 preferable is preferable. If it is lower than 8, the image density is not sufficient. If it exceeds 15, the replace of the toner by the regulating portion is so poor that image defect is produced in the solid white image. Furthermore, the magnetic chain is long, and therefore, the hair line uniformity decreases.
  • Embodiments 1 - 3 The following image evaluation has been made with respect to Embodiments 1 - 3 in order to check the superiorities of the average circularity which is not less than 0.965. Under the foregoing evaluations evaluation method a) -i) and A) -D), there is no difference among Embodiments 1 - 3.
  • the image evaluation with a larger load than with the foregoing image evaluation has been made. More particularly, 3000 sheets printing of lateral lines with print ratio 2% are intermittently carried out under the evaluation ambience of 32.5°C, 80% Rh.
  • the intermittent printing means printing one by one, which is different from the continuous printing in that pre-rotations and post-rotations of the photosensitive drum are carried out. Under these conditions, the toner, the regulating member, the elastic sleeve, the drum and the like are more easily deteriorated. In the intermittent mode, the evaluation have been made.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required and a stress exerted on the toner is low, so that even when the number of printing sheets is increased (particularly at a low print ratio), it is possible to considerably prevent a deterioration of the developer to suppress an increase in amount of fog due to the developer deterioration.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required, so that it is possible to considerably prevent a deterioration of the developer to suppress an increase in amount of fog by shaking a cartridge to mix the deteriorated developer and less deteriorated developer when the toner is short.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required and a stress exerted on the toner is low, so that even when the number of printing sheets is increased, it is possible to suppress such an image defect that agglomeration of toner is formed on the developer supply roller by frictional contact of the developer supply roller with the developer-carrying member to be moved and deposited in the halftone image.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of not less than 0.970 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • a developer which has been regulated in amount during the development has an amount per unit area of 5 - 14 g/m 2 and a specific charge of 10 - 50 ⁇ C/g, so that it becomes possible to effectively peel off and supply the toner to suppress development ghost.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of not less than 0.970 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • a developer which has been regulated in amount during the development has an amount per unit area of 5 - 14 g/m 2 and a specific charge of 10 - 50 ⁇ C/g, so that it becomes possible to effectively peel off and supply the toner to suppress an increase in fog amount due to toner deterioration and suppress development ghost. Consequently, it is possible to compatibly realize suppression of fog amount and ghost image defect.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of not less than 0.965 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • a developer which has been regulated in amount during the development has an amount per unit area of 5 - 14 g/m 2 , so that it becomes possible to effectively peel off and supply the toner irrespective of a change in specific charge to provide a uniform distribution of the specific charge in the toner coat layer, whereby it is possible to suppress solid white image defect.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of not less than 0.970 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • a developer which has been regulated in amount during the development has an amount per unit area of 5 - 14 g/m 2 to suppress solid white image defect and has a specific charge in a proper and wide range of 10 - 50 ⁇ C/g, so that it is possible to provide a wide margin for a fluctuation in specific charge, when the toner is deteriorated due to environmental change and change with time, thereby to suppress each image defect due to the fluctuation in specific charge.
  • the developer is one component magnetic toner having an average circularity of not less than 0.965 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a pressure exerted on an individual toner particle by frictional contact between a regulation member and the developer-carrying member or between an image bearing member and the developer-carrying member becomes uniform, so that even when the number of printing sheets is increased in a print mode more liable to cause toner deterioration, such as intermittent print mode, it is possible to considerably prevent a deterioration of the developer to suppress an increase in amount of fog due to the developer deterioration.
  • the developer is one component magnetic toner having an average circularity of not less than 0.965 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • the developer is one component magnetic toner having an average circularity of not less than 0.965 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a pressure exerted on an individual toner particle by frictional contact between a regulation member and the developer-carrying member becomes uniform, so that even when the number of printing sheets is increased in a print mode more liable to cause toner deterioration, such as intermittent print mode, it is possible to considerably suppress toner fusion on the surface of the regulation member.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of not less than 0.970 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • the developer is one component magnetic toner having an average circularity of not less than 0.970 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • the developer has an amount per unit area of 5 - 14 g/m 2 and a specific charge of 10 - 45 ⁇ C/g, so that it is possible to achieve an effect of further suppressing the image defect due to ghost, compared with Effect 5.
  • a ratio (B/A) of an iron element content (B) to a carbon element content (A), present at the surface of the above described developer, measured according to X-ray photoelectron spectroscopy is not more than 0.001, so that in a print mode liable to cause toner deterioration, such as intermittent print mode, an occurrence of damage of the regulation member, by the magnetic material present at the toner surface, due to frictional contact between the regulation member and the developer-carrying member can be considerably suppressed.
  • a ratio (B/A) of an iron element content (B) to a carbon element content (A), present at the surface of the above described developer, measured according to X-ray photoelectron spectroscopy is not more than 0.001, so that in a print mode liable to cause toner deterioration, such as intermittent print mode, it is possible to realize less toner deterioration and considerably suppress the development ghost even when the number of print sheets is increased.
  • a member to be developed is subjected to development with developer while applying a direct-current (DC) voltage as a developing bias (voltage) and pressing the developer-carrying member against an image bearing member as the member to be charged, whereby tailing of toner is suppressed, thereby to improve a thin line uniformity.
  • DC direct-current
  • a member to be developed is subjected to development with developer while applying a direct-current (DC) voltage as a developing bias (voltage) and pressing the developer-carrying member against an image bearing member as the member to be charged, whereby an edge of a high-density portion particularly on a downstream side of the process is developed with a high density, and an edge of a halftone portion adjacent to the high-density portion is developed with a low density.
  • DC direct-current
  • an image bearing member and a developer-carrying member are pressed against each other, so that a distance therebetween becomes small to increase an area on which an electric field or a magnetic field acts and a strength of the electric field or the magnetic field.
  • a distance therebetween becomes small to increase an area on which an electric field or a magnetic field acts and a strength of the electric field or the magnetic field.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required, so that it is possible to suppress toner deterioration due to returned toner, an occurrence of agglomerated toner grown from a contaminant contained in the returned toner as a seed, and a defect in halftone image due to deposition of the agglomerated toner on the developer supply roller.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required, so that even when the number of printing sheets is increased, it is possible to suppress such an image defect in halftone image occurring every full circumference of the developer-carrying member due to peeling-off and supply failure of the toner, caused by frictional contact between the developer supply roller and the developer-carrying member leading to residual paper dust, contained in the returned toner, remaining in the developer supply roller.
  • a member to be developed is subjected to development with developer while applying a direct-current (DC) voltage as a developing bias (voltage) and pressing the developer-carrying member against an image bearing member as the member to be charged, whereby it is possible to suppress an image defect in a solid black image due to white spots therein by suppressing leakage generated through paper dust contained in the returned toner in a high-temperature and high-humidity environment.
  • DC direct-current
  • one component magnetic toner having an average circularity of not less than 0.970 is used.
  • toner deterioration is accelerated by increasing the number of printing sheets particularly in such a print mode as intermittent print mode that an ununiform stress due to inclusion of irregular-shaped toner between the developer-carrying member and the image bearing member or between the charging means and the image bearing member is caused to occur and thus the toner is liable to be deteriorated, it is possible to suppress drum damage leading to a defect in halftone image occurring every full circumference of the drum.
  • developer has an average circularity of not less than 0.970, and a ratio (B/A) of an iron element content (B) to a carbon element content (A), present at the surface of the above described developer, measured according to X-ray photoelectron spectroscopy is not more than 0.001, so that it is possible to further improve Effect 24 of suppressing drum damage, thereby to further effectively suppress the defect in halftone image occurring every full circumference of the drum.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required and a stress, so that even when the number of printing sheets is increased (particularly at a low print ratio), it is possible to considerably prevent a deterioration of the developer to suppress an increase in amount of fog due to the developer deterioration.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required, so that it is possible to considerably prevent a deterioration of the developer to suppress an increase in amount of fog by shaking a cartridge to mix the deteriorated developer and less deteriorated developer when the toner is short.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required and a stress exerted on the toner is low, so that even when the number of printing sheets is increased, it is possible to suppress such an image defect that agglomeration of toner is formed on the developer supply roller by frictional contact of the developer supply roller with the developer-carrying member to be moved and deposited in the halftone image.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of less than 0.965 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • a developer which has been regulated in amount during the development has an amount per unit area of 8 - 15 g/m 2 and a specific charge of 13 - 23 ⁇ C/g, so that it becomes possible to effectively peel off and supply the toner to suppress development ghost.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of not less than 0.970 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • a developer which has been regulated in amount during the development has an amount per unit area of 8 - 15 g/m 2 and a specific charge of 13 - 23 ⁇ C/g, so that it becomes possible to effectively peel off and supply the toner to suppress an increase in fog amount due to toner deterioration and suppress development ghost. Consequently, it is possible to compatibly realize suppression of fog amount and ghost image defect.
  • the member to be developed is subjected to development with developer while the member to be developed is pressed by the developer-carrying member, and the developer is one component magnetic toner having an average circularity of not less than 0.965 and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member.
  • a developer which has been regulated in amount during the development has an amount per unit area of 5 - 14 g/m 2 and a specific charge of 13 - 23 ⁇ C/g, so that it becomes possible to effectively peel off and supply the toner, whereby it is possible to suppress solid white image defect.
  • a member to be developed is subjected to development with developer while applying a direct-current (DC) voltage as a developing bias (voltage) and pressing the developer-carrying member against an image bearing member as the member to be charged, whereby tailing of toner is suppressed, thereby to improve a thin line uniformity.
  • DC direct-current
  • a member to be developed is subjected to development with developer while applying a direct-current (DC) voltage as a developing bias (voltage) and pressing the developer-carrying member against an image bearing member as the member to be charged, whereby an edge of a high-density portion particularly on a downstream side of the process is developed with a high density, and an edge of a halftone portion adjacent to the high-density portion is developed with a low density.
  • DC direct-current
  • an image bearing member and a developer-carrying member are pressed against each other, so that a distance therebetween becomes small to increase an area on which an electric field or a magnetic field acts and a strength of the electric field or the magnetic field.
  • a distance therebetween becomes small to increase an area on which an electric field or a magnetic field acts and a strength of the electric field or the magnetic field.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required, so that it is possible to suppress toner deterioration due to returned toner, an occurrence of agglomerated toner grown from a contaminant contained in the returned toner as a seed, and a defect in halftone image due to deposition of the agglomerated toner on the developer supply roller.
  • the developer is one component magnetic toner and is attracted to a developer-carrying member by a fixed magnetic field generation means disposed in the developer-carrying member, whereby the developer is magnetically conveyed onto the developer-carrying member.
  • a developer supply roller for supplying the developer onto the developer-carrying member is not required, so that even when the number of printing sheets is increased, it is possible to suppress such an image defect in halftone image occurring every full circumference of the developer-carrying member due to peeling-off and supply failure of the toner, caused by frictional contact between the developer supply roller and the developer-carrying member leading to residual paper dust, contained in the returned toner, remaining in the developer supply roller.
  • a member to be developed is subjected to development with developer while applying a direct-current (DC) voltage as a developing bias (voltage) and pressing the developer-carrying member against an image bearing member as the member to be charged, whereby it is possible to suppress an image defect in a solid black image due to white spots therein by suppressing leakage generated through paper dust contained in the returned toner in a high-temperature and high-humidity environment.
  • DC direct-current
  • a developing device includes a rotatable developer carrying member for carrying a developer to develop an electrostatic image formed on an image bearing member with the developer; non-rotatable magnetic field generating means, disposed inside the developer carrying member, for magnetically attracting the developer on the developer carrying member; a regulating member for regulating an amount of the developer carried on the developer carrying member, wherein the developer carrying member is provided with a surface elastic layer, and the developer carrying member is press-contacted to the image bearing member, and wherein, the developer is an one component magnetic toner having an average circularity not less than 0.965, and an amount of the developer per unit area of the developer regulated by the regulating member is 5 - 14 g/m 2 , and an amount of electric charge thereof is 10 - 50 ⁇ C/g.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dry Development In Electrophotography (AREA)
  • Developing Agents For Electrophotography (AREA)
  • Magnetic Brush Developing In Electrophotography (AREA)
  • Developing For Electrophotography (AREA)
EP04029559A 2003-12-15 2004-12-14 Appareil de développement pour le développement sous pression et avec un révélateur magnétique à un composant Withdrawn EP1574911A1 (fr)

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US7233758B2 (en) 2007-06-19
CN100504639C (zh) 2009-06-24

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